The present invention is directed to a method for producing a semiconductor laser device having a hybrid dual laser design that achieves inter-laser spacings as small as 20 .mu.m. Such a device may be incorporated in numerous devices including optical disk readers or flying spot scanners (commonly referred to as raster output scanners (ROSs)). A flying spot scanner typically has a reflective multifaceted polygon mirror that is rotated about its central axis to repeatedly sweep one or more intensity modulated beams of light across a photosensitive recording medium in a linear or fast-scanning direction. Printers employing multiple intensity-modulated beams are referred to as multibeam or multispot printers. The dual or multispot lasers are considered to be an enabling technology for high speed printers operating at resolutions of about 600 spots per inch (spi). The present invention utilizes multiple asymmetric laser dies bonded p-side away from a heatsink to provide the multibeam output capability for a ROS. Furthermore, the small air space separating the two laser dies in the hybrid dual laser design provides thermal, electrical and optical isolation therebetween. To drive the lasers, electrical contact to the p-side thereof with a wire bond pad extending through the base from one side of the laser die.
Heretofore, the desirability of a multiple beam semiconductor laser has been recognized. However, because of thermal crosstalk, practical inter-laser spacings for the prior proposals are generally limited to spacings of at least 100 .mu.m. Designs intended to achieve close spacing of the emitted laser beams are known, however, of which the following disclosures which may be relevant:
U.S. Pat. No. 4,901,325, patentee: Kato et al., issued: Feb. 13, 1990,
U.S. Pat. No. 4,870,652, patentee: Thornton, issued: Sep. 26, 1989,
U.S. Pat. No. 4,796,964, patentee: Connell et al., issued: Jan. 10, 1989,
U.S. Pat. No. 4,403,243, patentee: Hakamada, issued: Sep. 6, 1983,
The relevant portions of the foregoing patents, hereby incorporated by reference for their teaching, may be briefly summarized as follows:
U.S. Pat. No. 4,901,325 teaches a semiconductor laser device used in an optical disk device which utilizes a pair of semiconductor laser chips and a fixing device for fixing the laser chips so that the electrode surfaces are approximately parallel and opposite to each other. The fixing device comprises either a single-piece, U-shaped block or, alternatively, a pair of blocks, upon which the photodiodes are ultimately mounted. When a pair of blocks are used, a tooling system (see FIG. 9) is used to align and permanently affix the blocks to a base plate under the control of a vision system which enlarges and processes an image region centered on the active regions of the lasers affixed thereto.
U.S. Pat. No. 4,870,652, discloses a monolithic high density array of independently addressable semiconductor lasers. The lasers are further characterized as having emitters on closely spaced, 3-10 .mu.m, centers, without displaying phase locking and with minimal crosstalk effects. The monolithic, independently addressable array is suitable for use with high speed laser printers, laser disk technology, and fiber optic communication.
U.S. Pat. No. 4,796,964 describes a method for using a multiple emitter solid state semiconductor laser in a raster output scanner. The overlapping beams are sequenced in ON/OFF operation to avoid any inter-beam interference in a manner that assures that only one laser beam will be on at any given time. Hence, nonuniformity caused by optical interference of overlapping beams is prevented without the need for further modification of the optical properties of the beams (e.g., polarization and wavelength).
U.S. Pat. No. 4,403,243 teaches a laser apparatus including support and soldering means for a light transmitting member which is affixed so as to allow transmission of an emitted laser beam generated within the apparatus by a semiconductor laser. The light transmitting member, by soldering, becomes hermetically sealed to a support member, thereby completely encapsulating the laser source.
In accordance with the present invention, there is provided a method of fabricating a multiple beam semiconductor laser having first and second semiconductor laser dies affixed to supporting heatsinks thereon. The method comprises the steps of laminating facing sides of the heatsinks on opposite sides of an intermediate material layer to form a sandwich, bonding the sandwich to a base, removing the intermediate material layer without disturbing the relative positions of the heatsinks, and permanently affixing the first and second semiconductor laser dies on facing sides of the heatsinks.
In accordance with another aspect of the present invention, there is provided a method of fabricating a multiple beam semiconductor laser. The method comprises the steps of forming a laminate including a layer of spacer material and a first heat sink, bonding the laminate to a base, placing a second heatsink in an abutting relationship with said base and the intermediate material of said laminate, bonding the second heatsink to a base, removing the spacer material layer from the laminate so as to space opposed facing surfaces of the first heatsink and the second heatsink from one another, and affixing a first semiconductor laser die on the facing surface of the first heatsink and a second semiconductor die on the facing surface of the second heatsink.
In accordance with yet another aspect of the present invention, there is provided a method of fabricating a mounting system for a multiple beam semiconductor laser, wherein the mounting system includes a pair of heatsinks located on a common base. The method includes the steps of laminating the heatsinks on opposite sides of an intermediate material layer to form a sandwich so that facing surfaces of the heatsinks are generally parallel and spaced apart by a predetermined distance, bonding the sandwich to a base, and removing the intermediate material layer without disturbing the relative positions of the heatsinks.